package com.zhaohg.algorithm;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Function: 两个线程交替执行打印 1~100
 * <p>
 * lock 版
 * @author zhaohg
 * @date 2018/12/28.
 */
public class TwoThread {
    
    /**
     * 重入锁
     */
    private final static Lock LOCK = new ReentrantLock();
    private int start = 1;
    /**
     * 对 flag 的写入虽然加锁保证了线程安全，但读取的时候由于 不是 volatile 所以可能会读取到旧值
     */
    private volatile boolean flag = false;
    
    public static void main(String[] args) {
        TwoThread twoThread = new TwoThread();
        
        Thread t1 = new Thread(new OuNum(twoThread));
        t1.setName("t1");
        
        
        Thread t2 = new Thread(new JiNum(twoThread));
        t2.setName("t2");
        
        t1.start();
        t2.start();
    }
    
    /**
     * 偶数线程
     */
    public static class OuNum implements Runnable {
        
        private TwoThread number;
        
        public OuNum(TwoThread number) {
            this.number = number;
        }
        
        @Override
        public void run() {
            while (number.start <= 1000) {
                
                if (number.flag) {
                    try {
                        LOCK.lock();
                        System.out.println(Thread.currentThread().getName() + "+-+" + number.start);
                        number.start++;
                        number.flag = false;
                        
                        
                    } finally {
                        LOCK.unlock();
                    }
                }
            }
        }
    }
    
    /**
     * 奇数线程
     */
    public static class JiNum implements Runnable {
        
        private TwoThread number;
        
        public JiNum(TwoThread number) {
            this.number = number;
        }
        
        @Override
        public void run() {
            while (number.start <= 1000) {
                
                if (!number.flag) {
                    try {
                        LOCK.lock();
                        System.out.println(Thread.currentThread().getName() + "+-+" + number.start);
                        number.start++;
                        number.flag = true;
                        
                        
                    } finally {
                        LOCK.unlock();
                    }
                }
            }
        }
    }
}